The thoracic spine refers to the upper- and middle-back. It joins the cervical spine and extends down about five inches past the bottom of the shoulder blades, where it connects with the lumbar spine.
The thoracic spine is made up of twelve vertebrae, labeled T1-T12. While the cervical spine is built for flexibility (e.g. turning the head) and the lumbar spine is built for power and flexibility (e.g. lifting heavy objects, touching the toes), the thoracic spine is built for stability. This stability plays an important role in holding the body upright and providing protection for the vital organs in the chest.
There are several features of the thoracic spine that distinguish it from the lumbar and cervical spine:
- Limited flexibility. The rib cage is connected to each level of the thoracic spine. One rib is connected firmly on each side of each thoracic vertebra, with one pair extending from either side of T1, another pair from T2, and so on. The ribs attached to T1-T10 curve around to meet at the front of the body and attach to the chest wall, or sternum. Combined, the thoracic spine and rib cage anchoring each level of the spine from T1-T10 provide both stability and a protected space for the heart, lungs, liver and other vital organs.The ribs connected to T11 and T12 at the bottom of the thoracic spine do not attach the sternum in front, but do provide protection for the kidneys in the back of the body. Because these levels have slightly less stability, they are slightly more prone to problems that can cause pain.
- Thinner intervertebral discs. Between each of the spine’s 24 unfused vertebrae are intervertebral discs, spongy pads that act as shock absorbers. In the thoracic spine, the intervertebral discs are thinner than at the cervical or lower spine. This adds to the thoracic spine’s relative inflexibility. Despite the thinner discs, it is still less common to have disc problems in the thoracic spine due to the limited flexibility.
- Narrower spinal canal. The cervical and thoracic spine forms a protected, hollow core for the spinal cord to pass through, called the spinal canal. This canal is most narrow in the thoracic spine, and therefore the spinal cord is at a risk for damage if a thoracic vertebra is injured.